In recent years, in the field of mobile terminals including a mobile phone and a tablet PC, there has been a problem of electric power consumption increasing due to, for example, an improvement in operating frequency of a CPU. Further, the mainstream of displays (liquid crystal display devices) mounted on such mobile terminals has been those having a resolution equal to or higher than high definition (HD). Electric power consumed by a mobile terminal in displaying an image is thus expected to increase more and more in the future.
Under such circumstances, attention has been drawn to a display technique that allows a high-resolution image to be displayed with reduced electric power consumption.
Electric power consumption of a liquid crystal display device basically depends on a driving frequency of that liquid crystal display device. Thus, as is publicly known, the electric power consumption can be effectively reduced in a case where the driving frequency is set at a low value.
In the field of display devices, liquid crystal display devices are most common. The mainstream of liquid crystal display devices has been those including, as switching elements for driving a liquid crystal panel, thin film transistors (TFTs) each including a semiconductor layer made of continuous grain silicon (CGS) or amorphous silicon (a-Si).
Such a liquid crystal display device is typically driven at 60 Hz. In a case where the liquid crystal display device is driven at a driving frequency of less than 60 Hz so as to reduce its electric power consumption, the liquid crystal display device carries out a refresh operation less often, and the TFTs have a longer off-period accordingly. The liquid crystal display device thus needs to keep respective voltages of pixel electrodes substantially constant over a longer period.
A TFT including such a semiconductor layer made of CGS or a-Si has a relatively large amount of a current leaking while the TFT is off. Thus, it is impossible to keep the voltage of a pixel electrode substantially constant for longer than a predetermined period while the TFT is off, with the result of a decrease in the voltage of the pixel electrode.
Thus, in a case where a liquid crystal display device includes TFTs each (i) including a semiconductor layer made of CGS or a-Si and (ii) having an off-period longer than a predetermined period, the liquid crystal display device suffers from a decrease in luminance and/or an increase in flicker occurrence, with the result of deterioration in display quality.
In contrast, attention has been drawn in recent years to a TFT including, as a semiconductor layer, an oxide layer containing at least one element selected from indium (In), gallium (Ga), and zinc (Zn), e.g., a TFT including an oxide semiconductor layer containing InGaZnOx. Such a TFT has a significantly small amount of a current leaking while the TFT is off, as compared with the above-described TFT including a semiconductor layer made of CGS or a-Si.
TFTs each including such an oxide semiconductor layer do not easily let electric charge leak from pixels while the TFTs are off. A liquid crystal display device including such TFTs thus do not have deterioration in display quality even in a case where the liquid crystal display device is driven at a driving frequency of less than 60 Hz.
As described above, a liquid crystal panel (hereinafter, referred to as “oxide semiconductor liquid crystal panel”) that includes TFTs each including an oxide semiconductor layer can be driven at a decreased driving frequency. This makes it possible to reduce electric power consumption as compared with a liquid crystal panel that includes TFTs each including a semiconductor layer made of CGS or a-Si.
A TFT including an oxide semiconductor layer, which is included in the oxide semiconductor liquid crystal panel described above, is also higher in electron mobility while the TFT is on than a TFT including a semiconductor layer made of CGS or a-Si. This allows the oxide semiconductor liquid crystal panel to include small TFTs for respective pixels and to have an increased aperture rate and an increased light transmittance.
With use of these liquid crystal panel characteristics, it is possible to reduce electric power consumed by a backlight, thereby making it possible to (i) reduce electric power consumption of the liquid crystal display device while maintaining a luminance equal to that of a conventional liquid crystal display device or to (ii) prepare, without causing a decrease in luminance, a liquid crystal panel having resolution higher than that of a conventional liquid crystal panel.
For the above reasons, in the field of displays (liquid crystal display devices) in which reduced electric power consumption is demanded, importance is expected to be further placed on the oxide semiconductor liquid crystal panel in the future.
There have also been many devised methods for transmitting high-resolution image data via a transmission path.
For example, in order to increase a maximum transmission capacity per unit time for image data, an additional transmission path is provided so as to enlarge a surface area of the transmission path, and/or a data transmission frequency is increased.
In a case where the surface area of a transmission path has been enlarged as described above, more image data can be transmitted in a single transmission process. In a case where the data transmission frequency has been increased, image data can be transmitted in an increased amount per unit time.
However, these methods each unfortunately require a mobile terminal or the like to have a larger frame size and/or larger electric power consumption.
Patent Literatures 1 through 3 each disclose a method for high-speed transmission of image data. However, these methods may increase electric power consumption and/or a mounting area.